Eccentric plug valves 69 have been available to industry for some time, and typically include, as shown in FIG. 11, a main body 76 having an inlet port 73 outlet port 74 and a plug 75 mounted for rotation about a shaft 80, so that a plug front sealing face 81 is eccentrically rotated to either close off or open flow through a valve seat area 82, which is the area bounded by outlet edge 86 and chamber edge 86a. Such valves 69 are used, for example, in wastewater, mining, fresh water, and many other industrial and HVAC services. Inlet port 73 is inlet circular opening 85a. Outlet port 74 is outlet circular opening 85b. FIG. 13 represents the same valve 69 as shown in FIG. 11, except that flow through the valve of FIG. 13 is reversed and the valve is rotated 180°
The plug valves typically have a long service life and are known for their reliability. Many of the valves 69 are sold for use in sludge and slurry services such as wastewater, ash, mining tailings, and other similar applications. Eccentric plug valves 69 generally include two types: wherein the rotatable plug 75 and mating seat 82 is either cylindrical or spherical.
Cylindrical plugs 75 are desirable and seal against a cylindrical seat 82 around a seal seat area 82. When the valve 69 is closed, a seal is created between the plug 75 and a typically nickel, or other corrosion resistant, seat 82. Oftentimes, the valves 69 have a restriction in their internal flow when open, because due to internal configuration the flow area may for example be only approximately 80% of the internal flow area of inlet pipe 17 and outlet pipe 17a for which the valve 69 is connected. The seat opening is the area surrounded by outlet edge 86. The plugs 75 are normally elastomer faced for tight fluid shutoff and for abrasion and erosion resistance. Valves 69 are often provided with a standard “face to face” length conforming to US and ISO standards for plug valves. “Face to face” is the length of a valve as measured from the face of the inlet flange to the face of the outlet flange.
Eccentric plug valves 69 are quite versatile. In most liquid service for example, it is recommended that the valve 69 be installed with the nickel seat 82 in the downstream location of the valve 69, as shown in FIG. 11. In the case of suspended solid service such as slurry and sludge, it is sometimes recommended that the valve 69 be installed with the seat 82 upstream and/or with shaft 80 axis horizontal, such that the plug 75 is raised above inlet pipe 17 and outlet pipe 17a centerline when the valve 69 is open, as shown in FIG. 13. This assists with keeping the plug 75 and bearings away from accumulated settled grit, fines and other debris that can accumulate in the bottom of a valve main body 76.
While the above valve 69 designs are quite useful, available industrial plug valve 69 designs, such as the examples shown in FIGS. 11 and 13, have typically had a restriction to the fluid flow that occurs due to restrictions in the flow area configuration of the valve 10, for example, the flow area of the valve is approximately 80% of the flow area of inlet pipe 17 and outlet pipe 17a in some designs.
One solution to this has been to install an oversized valve 69, so that the seat opening, sometimes referred to as the port area, of valve 69 will effectively be 100% or more of the flow area of inlet pipe 17 and outlet pipe 17a. However, this has the disadvantage that the oversized valve 69 is heavy, expensive, and may require a larger actuator which may also be more expensive, as opposed to a more desirable compact unit. Further, the oversized valves 69 will be made with a smaller flange but will have an increased face to face length. This reduces interchangeability of the valves 69.
Another disadvantage of the known plug valves 69 is that where they are installed in sludge or slurry service, the intersection (located at 99) of circular opening 85a and internal cylindrical wall 84, as shown in FIGS. 11 and 13, can sometimes form a partial wedge shaped dam that allows sediment and other debris to accumulate in the lower section of the valve 69 as noted above.
Accordingly, it is desirable to have an improved plug valve 69 with cylindrical seating that enhances fluid flow and/or ameliorates the buildup effects of suspended solids use.